The present invention relates to an armature for a miniature direct current motor (hereinafter simply referred to as a miniature motor). More particularly, it relates to an armature for a miniature DC motor which may enhance the motor characteristics by keeping an insulation performance between an iron core and armature windings at low cost.
A miniature motor has been extensively used in a wide field including a variety of equipments. There is a demand of the improvement in a heat resistance, machining workability, assembling workability or the like in addition to the reduction at cost and the enhancement of the motor characteristics.
In an armature to constitute a rotor which is provided in an interior of the miniature motor, armature windings (hereinafter referred to as windings) are wound around an iron core in the form of a coil. In order to insulating the iron core and the windings from each other, there are a variety of approaches.
For instance, there is one case in which epoxy resin coating, or the like, is applied to the iron core or there is another case in which the iron core is covered with a sheet or a molding material made of resin formed in conformity with a shape of the iron core (see Japanese Utility Model Application Laid-Open No. Hei 2-60475, Japanese Patent Examined Publication No. Sho 31-7964 and Japanese Utility Model Application Laid-Open No. Hei 5-70150).
By the way, in the armature, since the windings are wound on the iron core, it is likely that an insulation failure would occur at edge portions of both end faces of the iron core. In the case in which the above-described coating is applied in order to avoid this insulation failure, it is difficult that the coating material adheres to the edge portions which most need the insulation performance.
When the coating becomes thick for this reason, internal spaces of the iron core for winding the wire become small. As a result, there is a fear that a winding number of the possible windings becomes small and there is a fear that the characteristics of the motor would be degraded.
Also, when the coating material is sprayed, the coating is applied to portions which do not need the coating. In order to perform the coating which is thin with a high reliability in order not to reduce the winding number of the windings, a high technology equipment and a high technology are necessary.
On the other hand, in the case in which the iron core is covered with the above-described sheet or molding which is made of resin, a predetermined thickness is needed to some extent in view of the molding technology. As a result, the internal spaces become small so that the winding number is decreased and it is difficult to thin the miniature motor.
A heat resistance temperature of the resin which is the material for the sheet or the like is low in a range of about 120xc2x0 to 180xc2x0 C. Also there is a fear that the sheet is offset. In addition, when the sheet or the like is produced, scrap materials are by-products, accordingly there is a fear that an environmental problem is lead.
Japanese Utility Model Examined Publication No. Sho 31-12529 and Japanese Patent No. 2807534, and the like, disclose an arrangement in which insulators made of paper are provided on the iron core. However, these technologies are not directed to a heat resistance, a machining workability and an assembling workability. Also, these technologies are not directed to an arrangement for preventing an insulation failure at the edge portions by providing insulators at both end faces of the iron core.
In order to overcome the above-noted difficulties, an object of the present invention is to provide an armature for a miniature DC motor which may enhance the characteristics of the motor by keeping an insulation performance between an iron core and armature windings at low cost. Also, another object of the present invention is to elevate a heat resistance temperature of the armature.
An armature for a miniature DC motor, according to the present invention, constitutes a rotor provided in an interior of a casing of the miniature DC motor, windings of the armature being wound around an iron core in the form of a coil, wherein insulators, which are made of paper including at least ordinary paper and have an electric insulation property, adhere to at least portions, of both end faces of the iron core, on which the armature windings are wound so that the iron core and the armature windings do not come into direct contact with each other.
It is preferable that the insulators are either an impregnated paper in which a substance having a waterproof effect is impregnated with an ordinary paper or a laminated paper in which an ordinary paper and a thin plate made of resin are laminated to each other.
Incidentally, an armature for a miniature DC motor constitutes a rotor provided in an interior of a casing of the miniature DC motor, windings of the armature being wound around an iron core in the form of a coil, wherein insulators made of paper composed of a vulcanized fiber may adhere to at least portions, of both end faces of the iron core, on which the armature windings are wound so that the iron core and the armature windings do not come into direct contact with each other.
Also, an armature for a miniature DC motor constitutes a rotor provided in an interior of a casing of the miniature DC motor, windings of the armature being wound around an iron core in the form of a coil, wherein insulators made of soft resin film may adhere to at least portions, of both end faces of the iron core, on which the armature windings are wound so that the iron core and the armature windings do not come into direct contact with each other.
In this case, it is preferable that a material of the soft resin film is selected from a group consisting of polyester synthetic resin, low-density polyethylene, high-density polyethylene, polyamide, polypropylene, polyvinyl chloride and polyvinylidene chloride.
In the armature, it is preferable that, under a condition that the insulators are bent from edge portions of both the end faces of the iron core toward internal spaces, the armature windings are wound around the iron core through the insulators.
Incidentally, in the armature, the insulators may be made of thick paper and have substantially the same shape as that of the end faces at the portions of both the end faces of the iron core or have such a shape in order that the insulators somewhat project from the edge portions of respective end faces of arm portions and anchor portions of the iron core.